Self-limiting growth of transition-metal fluoride films from the reaction with XeF₂

Metal-fluoride thin films were grown by reacting XeF₂ with polycrystalline vanadium, iron, and copper surfaces at room temperature. X-ray photoelectron spectroscopy was used to ascertain that films of VF₃, FeF₂, and CuF₂ form on the respective substrates. The film growth initially follows the Mott-Cabrera rate law, but then levels off after a self-limiting thickness is attained. The sudden stop in film growth is attributed to the inability of the precursor molecule to dissociate at the surface when the insulator film becomes too thick for electrons from the substrate to transport through. Thicker films grow on iron and vanadium than on copper, which is attributed to different densities of states at the Fermi level.